There was an experiment done with some chickens in a centrifuge at 2G (2 times earths gravity)

Apparently they came out with thicker bones and muscles, and could jump higher and run faster than normal chickens.

EDIT: I found the following quote pulled from the book:

There was the hyper-g work done on chickens, for example, by Arthur Hamilton ("Milt") Smith in the 1970s. Milt Smith was a gravity specialist at the University of California at Davis who wanted to find out what would happen to humans if they lived in greater-than-normal g-forces. Naturally, he experimented on animals, and he decided that the animal that most closely resembled man for this specific purpose was the chicken. Chickens, after all, had a posture similar to man's: they walked upright on two legs, they had two non-load-bearing limbs (the wings), and so on. Anyway, Milt Smith and his assistants took a flock of chickens – hundreds of them, in fact – and put them into the two eighteen-foot-long centrifuges in the university's Chronic Acceleration Research Laboratory, as the place was called.
They spun those chickens up to two-and-a-half gs and let them stay there for a good while. In fact, they left them spinning like that day and night, for three to six months or more at a time. The hens went around and around, they clucked and they cackled and they laid their eggs, and as far as those chickens were concerned that was what ordinary life was like: a steady pull of two-and-a-half gs. Some of those chickens spent the larger portion of their lifetimes in that goddamn accelerator.

Well, it was easy to predict what would happen. Their bones would get stronger and their muscles would get bigger – because they had all that extra gravity to work against. A total of twenty-three generations of hens was spun around like this and the same thing happened every time. When the accelerator was turned off, out walked ... great Mambo chicken!

These chronically accelerated fowl were paragons of brute strength and endurance. They'd lost excess body fat, their hearts were pumping out greater-than-normal volumes of blood, and their extensor muscles were bigger than ever. In consequence of all this, the high-g chickens had developed a three-fold increase in their ability to do work, as measured by wingbeating exercises and treadmill tests.

I haven't had a chance to track them down, but supposedly these are the references:

I don't know, but when astronauts spend long periods of time at MIR, their muscles, and bone density are reduced. So I feel like, if you were placed in a high G environment rather than a low G one, your body should adjust too.

It is taken into account - when we get around to a manned mission to Mars (takes a few months to get there), the astronauts will have incredibly strict exercise regiments - not so much on the way there, because the gravity on Mars is weaker, but very much so on the way back, because they'll have to train back up while experiencing 0 Gs.

To everyone complaining that they can't make Dragonball Z jokes - if all the DBZ comments hadn't been deleted, there would be more parent-level comments about a cartoon than about the science behind the OP's question. /r/AskScience strives to maintain a high signal-to-noise ratio. If we allow people to make the same jokes that fill the rest of reddit, then these get upvoted past the legitimate answers. People come here because they can get in-depth answers to complex scientific questions. They can get jokes from the entire rest of reddit.

It's good to have a community with high standards and mods willing to enforce them. Though the community at TrueReddit (which is similar in size to Askscience) is pretty good about downvoting comments that don't contribute.

Different people have different ideas about what is signal and what is noise. It would be nice if reddit would split voting for intelligent and funny comments, ala Slashdot, and allow users to choose which type of comments they'd like to see. It's unfortunate that the only solution thus far is to simply delete posts.

From the sidebar: Keep discussion on topic and focused on answering questions scientifically.

It looks like, given that subreddits can have and enforce their own rules, "signal" has been pretty clearly defined. I agree that a multi-type system might be cool, but I feel like /r/askscience would just turn that option off. There are other great places for it.

I'm in favor of letting each individual make a decision for themselves. If you want to see only intelligent posts, you should be able to choose an option to only show those posts.

Imagine if that existed for all of reddit. You could read /r/IAmA without having to sift through memes and pun threads. To you, all of reddit would be as intelligent as /r/AskScience. It's amazing that you are so fervently opposed to a solution that would give you exactly what you want.

23 people upvoted my original post and 44 downvoted it. All I've ever said is that all 67 people should be able to have the experience they want. I haven't endorsed or opposed any particular experience. I haven't and wouldn't tell the 44 they shouldn't be able to have theirs.

It's sad that you are being downvoted just for disagreeing with me. Reddiquette is a forgotten art. At any rate, I agree with you in principle. Unfortunately, the reality is that we have to do what we have to do to keep scientific discussion from being flooded by off-topic talk. And while some people may enjoy those kinds of jokes, /r/AskScience was founded specifically to encourage in-depth discussion of these kinds of questions, and it's what makes us unique from most of the rest of reddit.

What's even sadder is that I never actually disagreed with you. I've been very careful about that because I'm not entirely sure what I want from the subreddit. I've only said that it would be best if people who want different things could have it at the same time. People seem to think I want to change their experience which they're perfectly happy with, but I don't.

Oh but it is so related. First thing I thought of, in fact. The second was Ogryns (a Warhammer 40,000 reference).

But I actually wanted to ask if putting humans in centrifuges like this would have significant negative effects. I know that we might experience things such as compressed vertebre (I assume that would cause problems?), heart problems, and high blood pressure (mentioned below). However, would the risk and problems posed at, say, 2 G's be enough to prevent this from being a viable training method for high level athletes and perhaps military personel?

If a comment makes a scientific point using humor, it will stay. I'd upvote, it in fact. I really appreciate when people educate through entertaining approaches. But things that are just jokes or memes don't belong here. And those are what get deleted.

more specifically, the upvoted bit "then maybe the people that read /r/science actually like it" is the bit that "ruins" our subreddit. I wouldn't call it ruining, but the point is that we can't necessarily rely on the community alone. We are moderators of conversation, we try too keep that conversation goal-directed. People upvote and downvote what they "like" and "don't like." But the point of voting is "what adds to the conversation" and "what detracts from the conversation." That's how votes should be used (read reddiquette if you don't believe me). People don't do that, so we have to step in and moderate that behaviour from time to time.

No, we will end up losing the people who weren't really that interested in the first place. This isn't a third grade science classroom where the instructor is good if he can entertain and educate. People come here to find relevant answers, not impertinent pop culture references. Maybe you should start a new subreddit, filled with science and puns or something, if you really think there is that large of a market for it. But nevertheless, that place is not here.

Agreed. The people who are interested in science are not going to lose interest if they're asked to stay on-topic. Hell, I would wager that there are just as many people who actually find the requiem of serious discussion to be a welcome change from the typical humorous and immature atmosphere that proliferates most of Reddit.

That's my personal experience, at least. When I found out that AskScience existed, I wept quietly in joy.

For you to say that it's for 3rd graders, is the exact reason why science education is on the decline in the United States, because idiots like you run science departments, and they take science very seriously, to the point where students learn from a young age, to hate science.

What? You're being absurd. Entertainment has a time and a place, but that does not mean that it needs to stick its nose everywhere. Whenever anyone complains about something on reddit, they are met with a flurry of "start your own subreddit" comments. Yet when one does, like r/askscience, and sets their own personal rules, they are pressured to change it to be more like every other subreddit. It's ok to be unique. And for the record, I am a student, and not in a science field. I am simply an average user who appreciates not having to wade through a bunch of nonsense before finding a relevant answer to a question.

Wow, if you don't like it, you downvote it. If a ton of people are upvoting a joke in the science section, then it deserves to be there, because people found it useful or entertaining. No need to a be a serious douchebag who doesn't enjoy himself.

I'd be interested in similar studies done for low-gravity situations, if anyone can find some. I recall reading somewhere that life on the moon or in orbit would be spectacular for people with heart conditions, but returning to Earth after a long stay would be next to impossible.

Also curious about how mammalian foetal development would be affected in an altered gravity environment.

The effects of low/zero gravity are well studied from our own astronauts spending much time in space orbiting. Astronauts must exercise daily to maintain proper muscle/bone density or they will shrink and deteriorate causing problems on their return to Earth.

Going off of this, could walking around 24/7 with ankle weights make any significant improvement in the muscles/bones of our lower body [and if so. how long would that probably take?] or is it just marketing for ankle weights

Going off of this, could walking around 24/7 with ankle weights make any significant improvement in the muscles/bones of our lower body

Unlikely. The difference compared to a planet with higher gravity is that your body doesn't support the extra weight, the weights only drag your feet down. Perhaps you would develop stronger hip flexors and calves by walking around with ankle weights, but that's all.

A much better approximation of the higher gravity situation would be to walk around with a weight vest all the time.

Makes you wonder about individuals who consistently wore heavy armor back in the dark ages. I'm not ashamed to admit there was a time in my life I wore ~50 lbs of chainmail for several days per month, and that was very taxing.

Do you know where I could find more details on this study apart from buying the book? I googled Physiological Changes Associated with Long-Term Increases in Acceleration but couldn't find the actual study.

You'd develop more muscle, but you would not change the way you grow cartilege. So you'd become "stronger" in that your muscles would develop more, but you'd experience joint problems- wearing them out faster than usual. You'd also stress your heart a lot, with the constant exertion, and if the higher gravity was yielding higher air pressure you'd have higher blood pressure as well.

I expect that in a sci-fi situation like this you'd have a great deal of back and knee problems and a higher rate of heart failure in this population. You'd also probably have them change their behaviors to become more sedentary. When you came back to the real earth you'd be okay, and probably atrophy those hypertrophied muscles unless you went straight into some constant workout routine.

Then your joints would be fine. (this was a question on an orthopedics/bio-mechanics final)
I have the book on my hard drive at home. I will reference later.

Basically, your joint development is limited after your adolescence. So, If you were born on the planet, you all good. This is because the increased force on your joints would have increased the load that they are developed for. Go back to earth one day when you get older and walla! super jointed man

Your body will adapt immediately. I would imagine you would grow shorter, so as to overcome how much your body needs to move with the extra gravity. With the higher blood pressure, probably your body would adapt to that if you developed there as a fetus. Definitely your respiratory system would adapt you for life over there. However, coming back, you might experience symptoms identical to those who have traveled high up into mountains. Acclimatization needs to take place.

As far as your joints, however, those are much more hardwired into your genetic code, and there is not much adaptation taht will be happening there (other than the initial not growing as tall as you would on Earth). So probably this would be the biggest issue of living there.

Your muscles, however, would be on par and you really wouldn't feel much of a difference than being here on Earth (except possibly getting tired quicker, since even though you have hypertrophied muscles, it is a lot more work and energy). You would require a lot more food intake probably as well.

Your body will adapt immediately. I would imagine you would grow shorter, so as to overcome how much your body needs to move with the extra gravity

What's the basis of this? I imagine it's possible that people will become shorter, simple due to physical compression. But I find it hard to believe that a person transported to such a planet would immediately (as opposed to the species adapting over generations) grow shorter in order to become more efficient in the high gravity environment.

Forgive the exaggeration, but it seems akin to claiming someone would immediately grow webbing between their fingers if exposed to water 24/7.

There are studies, that show that a part of final height of a person is variable based on where they grew up.

For example, people who grow up in higher altitudes, tend to be shorter and not grow as tall. This has a lot to do with slower maturation due to having a reduction in oxygen availability.

However, with a stronger gravity there would be a higher pressure, and more oxygen - so it would mean that you shouldn't grow any shorter. But, the basis (at least the way I see it) is that your body will have to spend a lot more energy to grow and to mature as well. Physiological adaptations done by your body - especially when they are done from birth - are really intriguing in terms of HOW MUCH it could change.

Height is something that would have immediate effects (next generation) because again, a huge portion of it is controlled not by genetics, but by environment. In a stronger gravitational environment, your body would adapt to move stuff around your body over smaller distances, so as to spend less energy, since most of that energy would be going to skeletal muscle so as to counteract the effects of gravity.

There are a lot of studies, I just can't cite them right now since I am supposed to be paying attention to something.

EDIT: Just to say why next generation - if you have already developed and matured, your height won't really change. But if you are growing and maturing right now, then there would be an effect since the variables are set in place NOW. That is why I meant next generation would be adapting in terms of height.

Oh and in terms of credibility, I am an undergraduate student with dual majors in Anatomy & Cell Biology, and Physiology.

I don't think "earth-like" implies higher oxygen content in higher gravity, it asumes that the pressure at sea level is 1 atm, and thus the density and oxygen content of the air at sea level is the same as earth, however what is defined as space would probably be closer (and the air pressure would drop off more quickly with altitude).

Gravity doesn't have to be directly proportional air pressure. Imagine an Earth with no atmosphere. The pressure would be zero, but the gravity would be the same. If you have the right amount of atmosphere on your more massive planet, then you could have the 1 atmosphere of pressure and 2 Gs.

Furthermore, with your third point about climbing a mountain. It would also depend on where sea level was. Sea level isn't some special constant value, it's just wherever the top of the oceans happen to be. If you took away Earth's oceans right now and let the air fill up the gap, you'd end up with lower atmospheric pressure in any given place.

Your height may change (PDF of a small sample study) as much as 2.8 cm a day under normal circumstances. This height change is mostly in the trunk, so clearly there is some give and take to our height and living in a higher gravity environment would only exaggerate those effects. You are tallest right before you get out of bed in the morning. A few hours of vertical gravity exposure removes some height.

Joint problems seem like a good bet. People who put more strain on their joints on earth tend to have them degrade and fail. Muscles can (and, if used, do) adapt but joints do not seem to do anything of the sort beyond the offloading possible by supporting muscles. This is an eternal problem in athletes, even with extreme measures it seems they will wear the joints down eventually. People carrying a lot of extra weight or otherwise overloading them (including time, simply living to 90 or so without doing anything abnormal seems to include hip/knee replacements/discards) also follow the same pattern.

I don't really see why. After all, a thin person on a planet with slightly higher gravity is likely to still weigh less than his fat twin on Earth. (consider that a 150 lb person moved to a planet with 10% more mass would only weigh 165 lbs)

There are different types of cartilage - hyaline, elastic and fibrous cartilage.

Hyaline is the most common type. Typically what happens in cartilage is that you have chondrocytes producing the matrix constantly. These areas are not very well supplied with blood. The matrix as you get older consists of less and less water (in general as you get older you have less and less water as a percent of your mass). The matrix consists of collagens and proteoglycans mostly.

The cartilage gets worn away as a joint is excessively used. Why that is, I am not entirely sure. Obviously there will be people who won't have such an issue, but a lot of them do. As the cartilage gets worn out, the bones suddenly have more friction in between them and even start grinding against each other. This as you can imagine leads to a lot of pain, and even further degeneration of the joints.

There are also conditions like arthritis/osteoarthritis which have inflammations in the joints - those wear out the joints even quicker.

I think someone else could probably shed more light as to the causes of cartilage degeneration (other than overuse of course).

You sure you've got your cause and effect in the right order? Cartilage doesn't heal very well. I would be shocked if one of the primary prerequisites of serious weightlifting was not unusually high cartilage development at birth. Chondrocytes- the stem cells which kill themselves to form cartilage- can't freely migrate through cartilage.

The following studies seem to indicate that cartilage can, under certain conditions, heal and become stronger in response to particular stimuli. If you've got time, I'd appreciate hearing your thoughts.

I'm not an expert but I don't think higher gravity would necessarily lead to higher air pressure. Air pressure is the force of the air above you pushing down. That force is proportional to the acceleration caused by gravity and the mass of the atmosphere. So you could mitigate higher gravity by having a less massive atmosphere.

Larger planets tend to have thicker atmospheres. But yeah, increased pressure isn't directly caused by gravity, it's just that higher gravity means a world usually hangs on to more atmosphere during planetary development (or at least, that's my understanding of it).

It probably would make your bones stronger, they would probably be thincker and denser, but that means nothing to your joints. Your joints are going to end up slightly tougher, but in the case of growing up in 2g, you're joints will not be able to handle twice the weight, they would need an increase in both thickness and area to do that, that's something that would require significant changes to your porportions and not just muscle and bone strength.

Do all of those health problems also affect people who work out regularly vs. people who don't? It seems like regular weight training isn't much different than "a planet with slightly higher gravity," unless the constancy of the latter is what makes all the difference.

A question on a related note: I just recently finished "The Moon is a Harsh Mistress." - MINOR SPOILERS AHEAD. A plot device mentioned frequently is that someone raised under lunar gravity (or a "Terran" who spent too much time on Luna) would be unable to return to earth without suffering severe health problems. Heinlein clearly indicates these adaptations to be permanent or near-permanent. Is there any truth to this? I.e., is there a reason why a 6x increase in gravity would be just too much for the body to take?

That's certainly plausible. An average person can handle about 5 times normal Earth gravity being applied vertically to them without blacking out (fighter pilots and astronauts train to be able to handle a bit more). You generally pass out because your heart isn't strong enough to pump enough blood into your brain at higher gravity levels.

NASA has also done some experiments where they've had people simply spend a few months lying down on a bed to simulate low-g environments. Those people require physiotherapy in order to walk again.

It's quite plausible that living on the Moon for an extended period of time would make you unsuitable to live on Earth again, at least without some major preparation to handle gravity again.

Yeah, blackouts in high-gravity situations come from insufficient blood to the brain. Blood vessels develop their muscular strength- with which they maintain blood pressure and flow- dynamically based on the tension put on 'em, just like any other muscles. If they were having to push around 1/6 the blood pressure for awhile those muscles would atrophy, and then have a hell of a time maintaining blood flow and pressure when you came back to earth.

Well, the human body does tend to change and adjust to zero gravity; with muscles, (including the heart) deconditioning and atrophying somewhat and bones losing calcium/strength. Soviet cosmonauts (who presumably were among the top physical specimens), but who neglected to diligently exercise in space (see pg 130), faced problems on their return and had to be stretchered away, though they did recover.
I don't recall if heinlein put a timeline or hard limit (Stuart la Joie?) before changes became life threatening.

It would be akin to living on earth, but with a weighted vest at all times. This is an imperfect analogy, as the weight would be distributed over the whole body in higher gravity, but a close approximation. Joint problems could be exacerbated by the sudden increased load, as well as circulatory and heart problems - it would have to push harder than it's used to.

However, for a healthy adult there should be no problem adjusting to slightly higher gravity over several weeks or months, and returning to earth you would find yourself stronger, especially in the legs and trunk, and probably be pretty goodat basketball.

Essentially you are saying that those people who train harder and work their muscles a lot, will have more circulatory and heart problems and joint problems---or are you saying that going to the gym is fine but being under high gravity pressure is not?

He mentioned the joint problems as a result of "the sudden increased load", where the extra weight was immediate and unexpected by the body, not really the same situation where you work out and put on muscle over a period of time.

Although to some degree, weight is weight, and 250 lbs of muscle is going to be almost as hard on your knees as 250 lbs of fat. The human body can certainly be improved by exercise, but there's a practical limit that we've evolved to, and packing on more muscle than that can really tax your joints and your circulatory system.

Hmm. You know, ever since I been working out in the last year for the first time, I've had more joint-related pain than ever before, and I'm only 22 and I'm not really fat at all, like 17% BF. :( I don't get it...

I'm saying that being suddenly plunged into a stronger gravitational field could exacerbate joint problems. If the joints were fine to begin with, I doubt there would be a problem. The heart might have more problems dealing with the sudden and irreversible increase in blood pressure, but as I'm not a cardiologist this is only speculation. However, it stands to reason that under additional strain, defects and conditions that had not yet manifested might become readily apparent.

Certainly, weightlifting is a major cause of joint injury, and many powerlifters retire because of joint or tendon issues even though their muscles might still have some growth potential.

Perhaps a better analogy would be back-country hiking. One variable, the weight of the backpack, seems to be the primary argument so far, with the caveat that you have to wear it all the time, not merely while hiking. The other factor is terrain; if everything is flat, not as big of a deal, but if there are lots of slopes or stairs involved, it represents an entirely different stress load.

It wouldn't be terribly different that walking around 50 kg overweight.

Some muscles would get stronger, but because of the difficulty and discomfort in physical activity, you'd want to move around less, resulting in a more sedentary lifestyle, decreased endurance and poor cardiovascular health. You'd be more prone to joint problems, and you'd need higher blood pressure in your circulatory system.

Why? Your heart is just a muscle and now it has to pump harder to keep the blood flowing. Surely it would become stronger over time just like any other muscle.

I think this whole thing is fascinating. I'd live in a centrifuge for a few months to test it out.

My theory is that I'd come out much healthier than before. Heart would be stronger, I'd generally be stronger and I doubt you'd get much joint problems for just a few months. It take fat arses years to develop bad joints.

It's not just a matter of a heart having to pump more blood through a larger volume. If that were the case, someone with 150kg of fat would have as healthy a heart as someone with 150kg of muscle.

When living unhealthily and maintaining a poor diet, a combination of the two do damage to the heart in the long term. The stress the heart goes through when being poorly nourished is far less when considering someone who is active and fit, even if they carry around as much muscle as someone of equal size with fat.

But yes, the general idea is that you would absolutely be stronger from having to endure higher gravity. And yes, joint problems wouldn't be immediate -- it takes time and gradual damage.

This is especially a problem for astronauts in microgravity for extended periods of time, such as the ISS crew. Bone density is a determination of stresses on the frame, and with lessened stress comes bone atrophy.

Cost effective to what purpose? The US has done low oxygen living quarters for Olympic training, so I would assume if there was sufficient result it would be being done. My thought is that you couldn't make one big enough to live in, and anything else means you are better off training with a weighted vest.

I have a similar question, I'll just post it here for now: If a group of humans were to migrate to another planet that was larger than Earth, and remained isolated, would they eventually evolve to be of a proportional size with the new planet (i.e., become giants)?

Thanks to the square-cube ratio, becoming a giant is exactly the opposite thing you want to be on a heavier planet. If you double the size of a human, the human's mass increases eightfold (width times height times depth) while the strength of their bones and muscles increases fourfold (width times depth). You'll effectively double the stress that your bones are under. If you're a 200lb male, imagine carrying an extra 200lb of weights around, all day, every day, forever.

As a slightly unrelated note, having the perfect distribution of elements sort of puts a damper on the idea of moving to another planet which is something Bill Bryson brought up in his book, "A short history of nearly everything".

Think about all the elements you need just a little bit of (but not too much) to survive: Potassium, Magnesium, sodium chloride (salt), calcium, iodine, zinc, iron, copper, etc.... and think about all the ones that kill you: arsenic, lead, mercury, not to mention the radioactive ones. We are actually pretty picky on having a very exacting balance of elements in our food, drink, and air.

Well, I think it's more the opposite. We are tuned to the ratios of minerals and things available on our own world, and have no capacity to deal with the things we never encounter in nature. The problem remains though.

What would happen is that you would lose bone density equal to the rate at which gravity is forced upon your person, in reality this bone density loss can never be recovered. You will shrink as well, losing an inch-3 inches from your height. You will experience weaker erections, and also most likely attain through overgravitons a hidden penis.

As Ambiwlans points out, scientists have done it with animals, dbe should not claim no one has researched it unless he is in the field and damn well knows someone hasn't. The question is a good one that scientists have thought about, and shouldn't be dismissed.

Anyway, answers like his are non-answers, I rarely upvote answers like that unless they add some new insight (e.g. explaining why the question is impossible to answer).